We mostly enjoyed our stay at Casa María Paz. The hotel is a beautiful 17th-century casona and is decorated stylishly, with nice areas to lounge in. Our room (Mercedes) was one of the cheapest and had no natural light and was a bit humid, but the small fan provided helped with that (though I recommend they invest in a larger one).
The bed, shower, and wifi were excellent and the location was very good, just six or so blocks north of the zócalo. The bathroom had a few shabby aspects: a single slightly tattered bath robe, a sink whose pipes easily came apart. The breakfast could also be improved, perhaps with some local pan dulce and more fruit.
The music that the hotel plays all day is ‘90s hits, which is odd.